1. Technical Field
This invention relates to the field of encryption systems and applications thereof and, in particular, to a telecommunications application in which a user may encrypt information prior to secure transmission to a remote destination.
2. Description of the Background Art
Two key encryption systems are known in which a user of the encryption technique secures data to be transmitted such that upon reception a second key is used to decrypt the encrypted data. A pirate intercepting the transmitted data is unable to decrypt the encrypted data without having access to the second key. One such standard for Internet security is advanced by a number of On-line Internet services and RSA Data Security who would want to unify "Secure HTTP" (developed by Netscape) and SSI (developed by RSA). RSA in partnership with Cylink, the partnership known as PKP, holds U.S. Pat. Nos. 4,200,770; 4,218,582, 4,405,829, 4,424,414 and 4,995,082. These patents describe a private key/public key system where the user maintains a private key and shares a related public key with those with whom he is exchanging secure information.
The United States National Institute of Standards and Technologies, N.I.S.T., has also recommended a private key/public key standard related to the PKP proposal known as the DSS (digital signature standard algorithm) encryption/decryption algorithm, described and announced in the May 19, 1994, FIPS PUB 186. N.I.S.T. holds U.S. Pat. No. 5,231,668 to Kravitz on the digital signature algorithm. Given a message m, the message m along with a signature comprising a public key value and a hashing value s are transmitted to the far end where they are tested to verify the authenticity of the message. A pirate who does not know the private key cannot alter any "signed" message.
Many entities have proposed applications software packages that may be purchased for use on personal computers for the purpose of providing secure data transmission. An example of one such package is the AT&T "Secret Agent" software package, a public key/private key form of encryption algorithm similar to the PKP proposal. Another package commonly used today is so-called pretty good encryption or PGP which is reasonably available to users.
There are many potential applications of two key encryption systems in data telecommunications generally. For example, these may be categorized as personal computer to personal computer, person to person, and telecommunications apparatus to telecommunications apparatus and combinations of these. For example, in an Internet link to a database service, the user typically is equipped with a personal computer and modem and the far end server is also represented by a computer. When a user is remote from their personal computer, the user, not having a keyboard or cursor, is limited to a limited keypad such as a two tone key pad or voice input. Also, the party to whom the user connects over telecommunications facilities may be equipped only with a caller identification display device. In these latter situations, for example, if the user is trying to assure the recipient that the data to be transmitted originated with the user, the facilities may be limited in how the user "signs" the data by encrypting it and identifying to the remote party how the data is encrypted and how to decrypt it. In many situations, a user would want to "sign" their name, credit card data, authorization for banking transactions and the like without having to resort to carrying around a personal computer with them.
Thus, all of the known proposals describe different forms of keys that may be used to encrypt data prior to transmission but fail to describe particular applications of such encryption techniques, for example, when the user is not equipped with a personal computer or other sophisticated equipment for transmitting data securely over telecommunications facilities. A user at a pay telephone terminal, for example, has limited means for encrypting data by "signing" it as his own to permit a recipient to verify its authenticity.